Investigating and mitigating protrusion-induced powder bed anomalies in laser powder bed fusion

Purpose This study aims to investigate the influence of protrusions, typical in-process defects arising on features like thin walls, overhangs and lattices on powder spreading quality in laser powder bed fusion (LPBF). The work aims to understand how surface irregularities from previous layers affect powder uniformity and packing, ultimately impacting part quality. Design/methodology/approach A parametric simplification model is proposed to geometrically characterize protrusions and analyze their effects on powder bed quality indicators. The Discrete Element Method (DEM) is used to validate the model and explore the relationship between protrusion parameters (height, shape) and powder distribution metrics. Additionally, physical experiments are conducted to support simulation results and observe powder spreading with recoater-protrusion interactions. Findings The study reveals that protrusions significantly disrupt powder packing, leading to localized anomalies during spreading. Geometric parameters, particularly protrusion height and peak width play a dominant role in influencing these disruptions. Reducing the recoating speed effectively diminishes the extent and severity of anomalous zones, especially for lower-height protrusions, thereby improving powder coverage and packing density. These enhancements contribute to minimizing downstream defects such as keyhole porosity during laser melting. Originality/value This research uniquely highlights the critical role of underlying surface defects on powder spreading. By combining parametric modeling, DEM simulation and experimental validation, the study offers actionable insights for in-situ control strategies to adapt recoating speed and enhance build quality in LPBF.